Automatic transmissions for vehicles are known in which an electronic control unit generates signals for the control of a plurality of actuators of hydraulic type coupled to a clutch and to a gear change and used to bring about the selection and engagement/disengagement of the gears and the opening/closing of the clutch.
Known automatic transmissions are provided with an electric pump which is adapted to pressurise, in a hydraulic circuit, an operating fluid (oil) which is then supplied to the actuators in order to provide the power needed to open/close the clutch and select and engage the gears.
It is also known that in automatic transmissions of known type there is no control of the speed of rotation of the electric pump; for this reason, in some operating conditions, the noise generated by the electric pump during its operation may be particularly intense and perceptible to the driver and/or the other vehicle passengers. For instance, in all the situations in which the noise generated by other members of the vehicle is low, the noise of the electric pump may be particularly unpleasant for the driver.
A number of solutions have been proposed to resolve the above-mentioned drawback, including:                using a pump characterised by internal members with very precise geometries;        using special materials for the connection joint between the electric motor and the pump;        installing housings of sound-absorbing material in the vehicle to cover the pump;        using supports of the “silent-block” type to secure the pump body to the vehicle frame.        
The proposed solutions, although not completely resolving the noise problem, introduce further component members and entail an increase in costs.